I have never questioned Norm Coleman's absolute right to take the recount to the election challenge phase. I also don't question whether Coleman sincerely believes that he could still win a second term. (I'm not buying his frequent recent statements that he is confident that if all votes are counted, and none are counted twice, he will win. This is a longshot, but perhaps not a prohibitive longshot.) (See "Smart Politics" blogger Eric Ostermeier rundown of many the possible motives for the continuation of the case.)

But the national Republican Party, and its donor base that is presumably making it possible for Coleman's high-priced legal team to stay on the case, have other incentives to keep the case going, one of which to deprive the Senate Democratic caucus of one vote for as long as possible.

There's no telling when some important matter in the Senate might be decided by a single vote. And, to cut to the chase, if the Republicans are trying to organize a party-line filibuster and the Minnesota seat is still vacant, the Repubs can sustain a filibuster with 40 of their current 41 members. If Franken takes the seat, the Repubs need all 41 votes.

There's a detail in the filibuster rule, which I confirmed over the weekend with Congress expert Steve Smith, that is relevant here. The rule does not require 60 votes to invoke cloture (thus breaking a filibuster). It requires three-fifths of the full Senate. When there are 100 senators, that equals 60. If there were two vacancies (as was the case on the first few days of the new session, because of the Minnesota and Illinois seats being vacant), the cloture number would drop to 59. But with the Senate strength at 99 (as at present) the three-fifths rule (three-fifths of 99 is 59.4) still requires 60,

(I have written before that the importance of the 60-vote "filibuster-proof" Dem majority can be overrated. I still think so. Not every vote is a party line vote (although the House Repubs did achieve 100 percent unity in last week's vote against the Dem stimulus bill, and although Senate Repub leaders claim to have support of all 41 members to block any effort to seat Franken provisionally before he receives a state certificatee of election). So 60 Democrats doesn't rule out a successful filibuster — unless they all vote together — and 41 Repubs doesn't guarantee a successful filibuster. The current math makes the two or three most liberal or non-ideological Republicans senators — Olympia Snowe, Susan Collins, Arlen Specter, maybe John McCain, among the most important members of Congress on these close votes.)

Smith, by the way, doubts that the upcoming big Senate votes on the stimulus bill will be the occasion for the first filibuster. The Senate Dems and Repubs have worked out rules for this bill to ensure that Repub amendments will be considered, and he doesn't believe Repubs want to be seen as using a filibuster to block the bill.

But if the Minnesota election contest lasts two or three more months, as Smith now estimates it might, "it's entirely conceivable that there will be several votes on which the Franken vote could prove pivotal, so, if by paying Coleman's legal bills, the national Republican interest groups are able to drag the case out for a few months, that's all to the good as far as they are concerned," said Smith, who lives in Minnesota but is on faculty at Washington University.

University of Minnesota Congress watcher Kathryn Pearson said the math is correct, but she isn't sure that the first filibusters, or the first one-vote margins, are coming up any time soon. Depends on the Senate agenda, Pearson said.

By the way, in case you missed it, there is another possible development that will cause a sudden change in the "filibuster-proof majority" situation. New Hampshire Sen. Judd Gregg, a Republican, is the leading candidate currently under consideration by the Obama Administration for the currently vacant secretary of commerce nomination. New Hampshire has a Democratic governor. If Gregg is nominated and resigns his seat (Senate Repubs say they will offer him anything necessary not to do that), and if N.H. Gov. John Lynch seizes the opportunity to appoint a Democrat (Senate Repubs are trying to get a deal in advance that Lynch will appoint a caretaker Republican), and if Franken ultimately occupies the Minnesota seat, and if no other Democrat dies, resigns or moves into the cabinet, the Dems would reach 60 seats after all heading into the 2010 election cycle. (I'm sure none of this occurred to Team Obama when the idea of Gregg for Commerce arose.)

One reason for Gregg to take the cabinet job, by the way, is that his Senate term is up in 2010, and New Hampshire has been blueing up over the last two cycles, so his seat is not that safe. (Although he is probably the New Hampshire Republican most likely to hold the seat, so if he departs the Senate, thinking ahead to the midterm election...

The New York Times reported over the weekend that Gregg is now considered the leading candidate for Commerce, but also that:

"Mr. Lynch and Mr. Gregg have talked about the situation throughout the week, Democratic and Republican officials in New Hampshire say, and the governor has said he is open to appointing a Republican to the seat. A main factor in whether Mr. Gregg accepts the commerce position, these officials say, is a commitment from Mr. Lynch that he strongly consider a Republican or an independent for the Senate seat."

Mid-morning update: Speculation that Gregg will get the cabinet post is up several notches. But New England Cable Network reports that Gov. Lynch will likely appoint Bonnie Newman, a Republican, a former Gregg chief of staff, and a prominent supporter of the Dem governor as a caretakerto to serve the last two years of Gregg's term with an understanding that she won't run in 2010. If true, that would deny the Dems the potential 60th member for this session. But it also means that in 2010 the Repubs will be defending yet another open seat in a blue-leaning state. Wash Post's Chris Cillizza notes that the Dems have a promising candidate ready to go and the Repubs have no obvious fill-in for Gregg.